'People thought I was a freak. I kind of liked that'

Vogue model, style icon and David Bailey's muse, Penelope Tree was the ultimate Sixties It girl. In a rare interview she tells Louise France about her charity work, the misery behind her privileged upbringing - and how the Dalai Lama saved her life

Penelope Tree has both a name and a face that are hard to forget. Yet for the best part of the past 35 years she has done her damnedest to stay out of the spotlight. During a brief, heady period at the end of the Sixties this American-born model encapsulated the style of the times. Eyes as lustrous as they were round, cheekbones on which you could balance a cup and saucer, a kooky, ethereal sense of style that both epitomised the mood and was all her own. When John Lennon was asked to describe her in three words he is said to have replied: 'Hot, hot, hot, smart, smart, smart!' For a while, when David Bailey was her boyfriend and there were front covers for Vogue in her modelling book, she was the It girl in a decade crowded with other so-called It girls with memorable monikers, from Twiggy to Cilla.

Bailey recently credited her with kick-starting the flower-power movement. It's a notion that strikes Penelope Tree as preposterous. She would describe herself as a mother and a writer. She might volunteer the fact that she works for two charities. The last words that would come into her mind are 'model' or 'style icon'.

'Never,' she says, sounding aghast. 'Never. That period seems completely irrelevant. It wouldn't even occur to me to mention it.'

She is 58 now. Still striking to look at, standing in her kitchen in west London in chinos and old school trainers, she has a cool, natural poise. At the same time she is the least model-like sort of person one is likely to meet. It becomes apparent that she is self-deprecating, hesitant, contemplative, unfailingly polite, more comfortable asking a question than answering one - though at the same time matter-of-factly candid.

'If someone asks me a question it is very difficult not to answer honestly,' she says. In an industry based on artifice, she has a transparency about her that is appealing but must have made life as a model miserable.

At first it appears as though she has led a gilded sort of existence: the daughter of wealthy parents, brought up in a well-to-do, impeccably connected set in America, spotted aged 17 at one of Truman Capote's infamous black-and-white balls, rung up the following day by the legendary Diana Vreeland at American Vogue. Yet all was not what it seemed. At 21 she had already had a nervous breakdown. 'I always felt as though I was falling, falling, falling,' she says now. A mysterious skin disease had resulted in scars that scotched any hopes of a top-flight modelling career. Three years later her six-year relationship with David Bailey fell apart.

'I was with this photographer whose great love was female beauty and I no longer fitted the bill in any way,' she recalls. 'I went from being sought-after to being shunned because nobody could bear to talk about the way I looked.' There is a tendency to look back at the late Sixties and early Seventies as a halcyon time of free love and swirly skirts, bare feet and sexual liberation. Tree remembers it differently. 'I think of the Sixties as being every man for himself,' she says. 'There wasn't the therapy culture that there is now and there was a huge amount of abuse of alcohol and drugs. But nobody thought it was terribly odd. It was perfectly fine to be tripping down the King's Road. It was acceptable to behave quite strangely and talk as if you came out of a Beckett play.'

Notwithstanding a recent Burberry campaign with Kate Moss, Tree rarely models any longer. The only time she looks at archive images of herself, taken by the likes of Bailey, Richard Avedon and Cecil Beaton, is when her children, 28-year-old Paloma and Michael, 18, are curious. Their mother was known for theatrical lashings of mascara, but if she's wearing any make-up when we meet, it is barely there. Her long fringe tends to hide those famous eyes. Her time is taken up writing a book of fiction for teenagers and working, free of charge, for two organisations, Lotus Outreach, which works with children in south east Asia, and the Khyentse Foundation, which promotes Buddhist scholarship.

She rarely does interviews and she is, at least to begin with, ambivalent and nervous. However, she wants to raise the profile of the causes that she's involved in so she's made an exception. Lotus Outreach was founded 12 years ago in California by her Buddhist teacher to help street children in India. At first it was 'a very small Band-Aid organisation', she says. 'Two mobile vans equipped with medical supplies, food, clothes, a doctor, a nurse and a teacher. Every day the kids would get to know where the van would be.'

The charity has since expanded and now works in different locations, most recently in Thailand and Cambodia where the focus is on sex-trafficked girls. In 2005, Tree visited 25 different projects in the two countries. It was a life-changing trip and one not without its dangers.

'It was one of the most devastating experiences,' she says. 'In Cambodia you realise very soon that this is a country that has been completely raped and people are still living in fear.' She talks vividly about the poverty she encountered, visiting refugee camps where sex trafficking is so common it has almost become accepted, where families are so desperate they will sacrifice one daughter to unscrupulous agents in the mistaken belief that her earnings will look after the rest of the family. In reality parents receive a fraction, if any, of the money that agents promise and if they do see their daughters again they are invariably emotionally and physically scarred. Many disappear forever and of the few who do eventually return home it is because they're HIV-positive and of no more use to their captors.

'I remember a village where, as a sex tourist, you could pick up a five- or six-year-old boy or girl. Camps where agents would offer families $80 for one of their daughters and then sell her on for $500,' she says, plainly still affected by what she saw. A staggering 600,000 to a million girls are trafficked each year in the region.

Lotus Outreach's work is deceptively simple: education projects for girls who have been sex-trafficked to teach them new skills; radio spots to alert families to the perils of trafficking; vans that tour villages warning young girls of the dangers. One scheme is to buy bicycles for girls in remote areas to encourage them to go to school. It's not that they don't want to walk the eight miles to get to their nearest classroom; the problem is that they risk being raped on the way.

Tree's motivation appears to be neither opportunistic nor self-serving. She sits in the sunny, peaceful front room of the house where she lives with her second husband, and speaks knowledgeably about the issues. There are pictures of the Dalai Lama on shelves; several Buddhas silently watch over us. She drinks tea from a 'Free Tibet' mug. For some years now she has been a practising Buddhist, which entails daily meditation and study. In the mid-Eighties, at a low point in her personal life, almost undone by anxiety, she found herself in the front row of an event with the Dalai Lama. Along with many others, he briefly shook hands with her at the end. It would turn out to be the beginning of a new phase for Penelope Tree: over the next few years, life began to make a little more sense.

There may have been a few carefree interludes until that point, but for the most part she had been buffeted from one period of depression to the next. Her childhood sounds like something out of a particularly bleak Henry James novel. 'It was poor little rich girl, it really was. It was a funny way to grow up - but the visuals were good,' she says, keen to play it down but at the same time inherently unable to dissemble.

Her father, Ronald Tree, a wealthy Conservative MP and confidant of Winston Churchill, was 53 when she was born. (Penelope would be 41 and at a party in Sydney when someone casually informed her that he had been gay.) Her mother, Marietta Peabody, was an American socialite who would eventually come to represent America at the United Nations. As a young woman Marietta famously predicted for herself a life of 'parties, people and politics'.

At first the family lived in England but Marietta swiftly grew bored with provincial life so when Penelope was a child her father moved the entire house - 'Brick by brick?' 'No,' she replies, with a twinkle, 'servant by servant: the butler, the maid, the cook and the chauffeur' - to New York. Not long afterwards he, in turn, moved to Barbados. His daughter would see him in the school holidays. She describes her father as a 'renaissance man'. In Barbados he established the National Trust and the botanical gardens and wrote books. 'I felt married to him in an odd sort of way. I was married to him and my mother was this rather annoying person who came back every so often to lay down the law. We were probably too close. I certainly felt very protective of him towards her.'

Her mother, Tree says, took advantage of her father's wealth. 'People used to say, "God, your mother is one of the most amazingly beautiful people we have ever met, God you are so lucky". And yes, she accomplished many things and lots of men fell for her,' she pauses. 'But she was a crap mother, unfortunately. We had a very tough time relating to each other and although I can genuinely say without any bullshit that I have inherited her strength, I do often wonder what it would have been like to have a loving mother... Or even a mother.'

Marietta, whose own mother in her turn had been undemonstrative and tough, was never around. 'I lived in the nursery and my mother had lots of affairs,' Penelope says bluntly. She was virtually ignored. It was a buttoned-up household; nothing was talked about. Or if it was, as she grew older, it swiftly escalated into an argument. Marietta had a long relationship with Adlai Stevenson, the 1952 Democrat presidential candidate. When he died suddenly, her mother beside him, Penelope, 15, realised that Marietta was devastated but she felt protective towards her father. 'I felt angry with her for obviously caring for another man so much. It was all very confusing,' she says.

Her childhood sounds lonely but at the same time there were periods when she enjoyed huge freedom. Aged seven she already knew how to get around New York on her own. In her early teens, before her parents found out and sent her to a strict boarding school, which she hated, she would forge their signatures and sneak out to folk festivals. 'I knew all about Bob Dylan, I was in love with Joan Baez. I was tuned into that world.'

Tree was 13 when the legendary photographer Diane Arbus came across her - she cannot recall how - and photographed her for a feature for Town & Country magazine. She groans. 'It was torture, the whole thing. Now I know why everyone in her pictures looks like they do - because they have had to spend three hours with Diane Arbus staring at them.' It was a broiling August day, she was dressed top-to-toe in riding gear and told to lie down in a field. 'Now I know what she was trying to get: spoilt rich kid looking absolutely desperate in her own native habitat,' she says. When her father saw the images he was hopping mad and forbade them to be used.

Being a photographer's model may have remained a one-off diversion if she hadn't been homed in on by the grande dames at American Vogue. While she'd begun to cultivate her own style - she'd get furious reactions in the street of New York for her barely-there minis and racoon-tail skirts - what she hoped to do was go to college to study English literature. A shoot by Richard Avedon changed all that ('She's perfect. Don't touch her,' he said). Few arrestingly beautiful teenage girls would have been able to resist the attention and anyway, the sudden change of direction had an upside - she thought it would be an escape route from her background.

'I look back at his pictures of me and think that person knew more than I do now. It wasn't about looking desirable or pretty, he liked the inward-looking face. I put into those photographs all the things that I loved and that great yearning I had at the time to break away and be different from my family. I had a feeling I was going to fall in love with somebody and that was very exciting.'

Not long afterwards, who should come along but David Bailey, a boy from the East End, brought up largely by his single mother, who had tried his hand at being a carpet salesman and window dresser before turning to photography. The story goes that Tree did a shoot for British Vogue and the editor, Beatrix Miller, informed the British photographer that he was on no account to go near the ethereal, strange-looking girl from New York. Not least because he was married already to Catherine Deneuve. Deneuve, however, had already sensed trouble. She reportedly told her husband when she saw his pictures: 'You're going to run off with that girl.'

'I didn't see him for almost a year afterwards,' recalls Tree. 'But there were sparks between us and I thought about him all the time. And then he turned up in New York ... and that was kind of it.' She was 18; Bailey, as she calls him, was 30.

'I fell madly in love. Bailey kind of fitted the bill for me. I thought that he could save me from my parents and from the upbringing I had had.'

Because he came from a different background to you? 'No, it wasn't that he was working class - I really loved him as a person,' she replies. 'Often you look back at people you were infatuated with and realise you fell in love with a thing, not a person. I don't feel that about him. But I was much too young. I didn't know how to be in a relationship. And I was very unsophisticated. He was my first boyfriend really. I was quite backward in lots of ways. I didn't look it but I was.'

For a year or so the relationship worked out. They lived together, travelled the world. When they were in London the photographer and his muse were at the epicentre of Sixties society.

'But then the girl thing came up,' she says frankly. 'I kind of clung to him like a koala to a eucalyptus tree. Even though I think he quite liked it in a way, inevitably it became claustrophobic. It was like being on the shore and watching somebody drift away.' She was jealous and somehow obsessed with the idea that she should behave like a character in a 19th-century novel.

'What an idiot!' she laughs at herself now, particularly at the notion that she was monogamous while Bailey, presumably, was not. 'I had this Jane Austen view that once you have found your man, that is it. I don't know where that came from. Certainly not my mother.'

Her look at the time was described as part Pippi Longstocking, part Egyptian Jiminy Cricket. She herself played up what she described as her Martian-like appearance by shaving off her eyebrows. None of this does justice to the enigmatic luminosity that she brought to photographs but might indicate just how odd she appeared at a time when most models looked exactly the same. There are fashion observers who now say that she was a pioneer - she changed the notion of beauty and, like Kate Moss for this generation, brought her own sense of style to the party that other people copied.

Typically, Tree is quick to deflate this kind of praise. 'I felt quite fraudulent because I am not a classic beauty,' she says, 'not now, not then. Like lots of models I felt insecure about the way I looked. We know too well that it's a lot to do with disguise and how you put yourself together.' She describes slogging around agencies with her book as like 'being a piece of meat. They would discuss your body as though you were not there. But I was a model and that is what you do.'

While there were photographers who adored her, there were others who refused to work with her. 'They thought I was a freak in some way. I kind of liked that. I felt I was an alien so I didn't see anything wrong with looking like one.'

The alien metaphor is an apt one. She was in a strange country, surrounded by predatory women who she thought, probably quite rightly, were after Bailey. Plus she was secretly suffering from anorexia. She'd started not eating as far back as boarding school and was in the habit of weighing herself every day. 'I was absolutely controlled about it. I never went beyond a certain point because I didn't want to end up in hospital.' She deliberately never dipped below 100 pounds. 'Skinny for my height,' she says. 'But not starvation levels.'

Her son has told her that she is lauded as a role model on some pro-anorexia websites, which horrifies her. The idea that her boyish hips and narrow shoulders and flinty cheekbones helped her to get work strikes her now as deeply ironic, and scary. 'Anorexia is about not accepting who you are as a woman. It's an illness about ambivalence,' she says. The anorexia would turn into bulimia in her twenties: 'Talk about ambivalence: stuff yourself full of food and throw it up because you cannot bear having it inside' - and she was not able to surmount it until she was in her early thirties. It's an illness she still reflects on a great deal in a bid to understand it: she has written an introduction to a self-help book for parents of anorexics.

Just when it must have felt as if everything was going wrong, not least the relationship with Bailey, which was in freefall, and her career, which had been derailed by severe late-onset acne that left her face swollen, it got worse. She was arrested during a drugs bust for possession of cocaine. Scarred and looking rough, she bore no resemblance to the kind of woman who might find herself on the front cover of Vogue. The police, holding her in custody for the night, refused to believe that she was either a famous model or the daughter of wealthy parents who could easily afford bail. 'In a way, I was stripped of my identity completely,' she says.

Not long afterwards, Bailey went off with somebody else for the last time. 'I twigged and I left.' It was 1974.

For Tree, that intoxicating and yet nightmarish era was over almost as quickly as it had begun. For a while she travelled around the world 'on the dregs of the money I made modelling'. A period living in Los Angeles followed and then she moved to Australia with her first husband Ricky Fataar, a musician with the Beach Boys, and had her daughter, Paloma.

Motherhood has plainly been a source of solace, and a revelation. 'I never thought I would have a child but I am very very glad that I did,' she says. 'Because of the experiences I had had with my own mother, I had never even held a baby before. I was lucky - I adored my daughter immediately. It was a big thing for me. My mother had a hard time with her mother. My grandmother with my great-grandmother. It goes back four generations and I have broken that. '

For years she explored all kinds of spiritual paths, from ashrams in India ('We won't go into those,' she says firmly) to transcendental meditation to yoga. She discovered Buddhism in the Eighties at a point when she was surrounded by friends who were dying from Aids and struggling to deal with her own debilitating fear and grief.

The woman I meet seems sanguine but this peace of mind, if that is what it is, has been hard fought for. 'In reality no sooner is one old issue understood then another one arises,' she says, 'and hopefully not four at once. I'm pretty sure this is true for everyone... But I haven't had a drab life, that's for sure.' How has her Buddhist practice helped? 'I try to see what the priorities are and not get terribly fussed about things that don't matter. Not be swept away by feelings and emotions, which is my tendency,' she replies. 'Having said that, I probably will in the next 10 seconds.'

She was a researcher on a documentary series in Australia with Richard Neville, the infamous Oz publisher, when she met her second husband who is a Jungian analyst. Finally, perhaps, someone she can talk to, and who can listen. They've since returned to London and live a quiet, unstarry sort of life. She is not interested in a ritzy social diary, she says, although Bailey, remarkably, remains a friend (he agreed to do the photoshoot for this interview). 'There were a few years when I didn't want to be around him but the connection is still very strong,' she says. 'I've learned how to stand up to him. I wish I had then.'

For a while back then it looked as if she might be one of the casualties of the Sixties. She is, in fact, one of its more elegant survivors. I wonder what she thinks when she looks at her face in the mirror. 'I feel like it has all gone but you might as well live,' she replies, and laughs. I think afterwards that it is a very Penelope Tree sort of reply: self-deprecating, and really rather wise.